The present invention relates to a method of initializing a system for open/closed-loop control of the operational sequences of a motor vehicle and to a corresponding system.
A method of initializing an electronic control system, in particular in a motor vehicle, is known from German Published Patent Application No. 42 03 704 A1. The electronic control system contains a primary controller and a plurality of downstream secondary controllers, each one associated with a function module. All controllers are capable of exchanging information via a data bus. In the method described for initializing the control system, the primary controller is activated to successively perform program-controlled, selective initializations of all secondary controllers. During this initialization, each function module is activated to perform a predefined action which is localized with the help of an external application diagnosis. Thereafter, the discrete location where the function module, i.e., the associated secondary controller, is used is transmitted to the primary controller.
The method described in the above-mentioned document allows an initialization of an electronic control system, in which the use location of the function modules associated with the secondary controllers is identified using software means.
Controllers are used for the open/closed-loop control of the operational sequences of a motor vehicle. Normally, at least one controller is associated with each function unit in the motor vehicle, for example, the engine control. It is, however, also possible to combine the control of a plurality of function units in one controller or to provide a plurality of controllers for complex units.
Each of the controllers is connected to a number of sensors for receiving data which will be needed for calculating the control signals. It is known that the sensors can be connected to the controller via a cable harness. This means that each data line connects exactly one sensor to the controller. Hard wiring via a cable harness allows the sensors to be uniquely assigned to the controller. However, it is disadvantageous in that the complexity of the wiring increases with an increasing number of sensors. This increases the costs and makes subsequent system modifications difficult.
In order to simplify the wiring in the vehicle, the sensors are connected to the controller via a single data bus. However, if a plurality of identical sensors are connected to a controller via one data bus, the controller must be able to uniquely identify these sensors.
For example, in a dual exhaust system, two lambda probes are needed for lambda control. These are connected to an engine controller via a CAN bus, for example. The lambda probes advantageously perform local evaluation of the measured signals, for example, by averaging. The pre-evaluated signals can then be forwarded via the CAN bus to the controller in a specific time grid such as an angle grid, for example.
It is known that sensors of different types can be used in order to permit unique assignment of the sensors. This, however, has been proved to be expensive. In order to keep the variety of parts as low as possible, the two probes used in the example described above should be identical whenever possible regarding their probe elements, software, connectors, and attachments.
If identical sensors are connected to a controller via one data bus under the above-described conditions, these sensors normally have the same identifier and the same priority for transmitting a message. As a result, unique assignment of the sensors in the controller is not possible. Therefore, the controller cannot determine from which of the sensors a received message originates and where each sensor is located. Thus, if a plurality of identical sensors are to be connected to a controller via one data bus, the sensors must be uniquely identified.
Taking as an example the lambda control in the case of a dual exhaust system, lambda probes with the same requirements may be used on both right-hand and left-hand sides of the exhaust system. Both lambda probes are then connected to the controller via the CAN bus. If the right-hand and the left-hand probes have no distinguishing features, both lambda probes are identical for the controller. As explained above, identical probes have the same identifier and the same priority for CAN transmission. This means that the controller cannot tell whether the message comes from the right-hand or the left-hand probe.
Therefore, the object of the present invention is to provide a method and a system which allow essentially identical sensors to be uniquely identified.
The method according to the present invention initializes a system for open/closed-loop control of the operational sequences of a motor vehicle. This system has a controller which is connected to a number of sensors via a data bus. The sensors are subdivided into groups with sensors of the same type in each group. This means that all the sensors in one group are identical. The controller has information about the sensor types used. If sensors of only one type are used, only one group is provided. The method is distinguished by the fact that, in order to initialize the system, a transmission request is initially transmitted to sensors of the same type. Thus, if sensors of only one type are provided, the controller only sends one transmission request to all the sensors. The sensors that receive this transmission request transmit a response to the controller staggered in time with the aid of suitable means. During the transmission of the responses staggered in time, the responses are overwritten by the controller with a sensor-specific identifier and a corresponding transmission priority.
Whenever the vehicle is started, including first start-up, a query is performed for the identity of the sensors. If identifiers with corresponding priorities have already been assigned to the sensors, all the sensors of the same type identify themselves consecutively with their identifiers. If the sensors have their original identifiers, which are the same, as is the case at the time of the first startup or after the sensors have been replaced in a repair shop, the sensor-specific identifiers are reassigned.
The controller overwriting the responses or messages from the sensors offers the advantage that the controller is aware of all the sensor-specific identifiers according to the program status and assigns them consecutively to each sensor during the responses by correspondingly overwriting the identifier (data field). Furthermore, during the transmission of the overwrite message or response, each individual sensor is aware of this transmission. This means that each sensor can assign itself the identifier overwritten by the controller and store it locally. In this manner the sensors can be uniquely identified.
The identifier is a file, for example, which contains information regarding the given sensor and characterizing it. Each sensor is assigned its own transmission priority. In this manner it can be ensured that, when a plurality of sensors transmit at the same time, the transmitted signals are received by the controller in the order of their urgency.
The sensors preferably have a random number generator as suitable means for ensuring that transmission of their responses to the controller are staggered in time. This ensures that sensors of the same type respond to a transmitted message of the controller at different times. After receiving the transmitted message, the corresponding random number generator of each sensor that has been addressed is started. It triggers the transmission of the response. The responses are thus sent staggered in time and received by the controller at different times. With this measure, feedback from the sensors is staggered in time and can be implemented in a simpler and more reliable manner.
It is advantageous if the results of the overwrite with the sensor-specific identifier and the corresponding transmission priority are stored in a non-volatile memory. In this manner, after restart of the vehicle, the complete process of assigning the identifiers to the respective sensors does not need to be carried out again.
After the sensors have been identified, they can be assigned according to their respective locations. This can be accomplished by comparing the signals delivered by the sensors with test signals. If the measured signal is identical to the test signal, the sensor can be assigned to a certain location. The test signal is transmitted consecutively to all locations. Thus all sensors can be assigned to their respective locations.
A CAN bus is preferably used as a data bus. The CAN bus has been successfully used in motor vehicles in particular.
The system according to the present invention for open/closed-loop control of a motor vehicle has a controller which is connected to a number of sensors via a data bus. Sensors of the same type or different sensors can be used. The sensors are divided into groups each containing the same type of sensors. The system is distinguished by the fact that the sensors have suitable means to ensure feedback from the sensors is staggered in time.